Some propellers, such as the prop fan, utilize thin, high solidity factor blades. The shape of the airfoils defining the blades allow high power loading with minimized compressibility losses. For instance, the prop fan blades manufactured by the Hamilton Standard Division of the United Technologies Corporation each have a power loading of approximately 37.5 shp/d. Such thin blades allow a prop fan propeller to achieve a peak efficiency of over 80% at a 0.8 flight Mach number, a tip speed of 800 feet per second, and an altitude of 35,000 feet.
The blades must be designed to perform reliably at such high tip speeds and Mach numbers. However, thin blades comprised of, for instance, NACA Series 16 airfoils have several design constraints. The shape of the leading edge of such airfoils makes a blade susceptible to foreign object damage. The shape of the trailing edge makes the blade very difficult to handle. The thin nature of the blade makes the blade difficult to construct.
U.S. Pat. No. 4,834,617 to Wainauski et al entitled "Airfoiled Blade" (commonly owned by the assignee herein and hereby incorporated by reference) shows a propeller blade having a plurality of particular airfoil sections. Such a propeller blade is relatively easy to handle, has a leading edge which is less susceptible to foreign object damage and is thicker to allow relative ease of construction. Moreover, the propeller blade disclosed in Wainauski performs within the desired flight envelope achieving the desired power loading and achieving the desired efficiency. However, the camber and thickness of the particular airfoil sections may not be modified for other flight envelopes in which such a blade may be utilized.